An epichlorohydrin-based rubber material has widely been used as parts of office automation apparatuses by making use of specific ionic conductivity thereof. Further a reduction in resistance and a reduction in hardness have been required to parts of office automation apparatus. Electrophotographic equipment applications will be described below as an example of a semiconductive member. However, applications of the present invention are not limited only to electrophotographic equipment applications.
In image forming apparatuses such as electrophotographic equipments, a direct contact charging system has recently employed as a means to charge a surface of a body to be charged of a photoreceptor, a dielectric or the like. In the direct contact charging system, a surface of a body to be charged is charged by directly bringing a charged member applied with voltage into contact with the surface of a body to be charged. The charged member to be generally used is a roller in which a semiconductive elastic body layer is formed on an axis of a mandrel made of metal or the like.
It have hitherto been known, as a method for forming a semiconductive elastic body layer, a method in which an electronic conducting semiconductive composition having semiconductivity by blending conductive particles such as carbon black, and a crosslinked rubber product are used, and a method in which a polar rubber per se having semiconductivity, such as an epichlorohydrin rubber or a nitrilebutadiene rubber is used (see Patent Document 1).
In the method in which a semiconductive composition using a polar rubber having semiconductivity, and a crosslinked rubber product are used, there is known, as a technique to cope with a reduction in hardness, a method in which a liquid rubber is blended so as to reduce hardness (see Patent Document 2).
However, in the method in which an electronic conducting semiconductive crosslinked rubber product having semiconductivity by blending conductive particles such as carbon black is used, it is difficult to control the hardness of a rubber composition. Also in the method in which a polar rubber per se having semiconductivity is used, there are requirements for further reductions in resistance and hardness. Thus, a problem to be solved is that it is difficult to reconcile both requirements and design freedom is low.